The present invention relates to heat management systems, and more particularly to a high efficiency heat transfer system for transporting heat to and from a plurality of heat sources and/or heat sinks utilizing liquid-vapor phase change of a working fluid in a monogroove heat pipe assembly. Although described in the context of spacecraft and space station applications, the present invention has substantial utility as well in terrestrial applications.
The thermal management of large orbiting spacecraft is expected to utilize two-phase heating and cooling loops which require heat transfer devices that can transfer heat both to and from other other fluid heat transport loops. The monogroove liquid heat exchanger has the potential for accomplishing this, particularly if a way can be found for effectively counteracting the tendency, under some operational conditions, of the monogroove heat pipes in the heat pipe assembly to either flood or dry out.
Prior efforts to solve these problems have not been entirely satisfactory. For example, in one design liquid was pumped directly into the monogroove legs through a valve under the control of an ultrasonic sensor located on one of the legs of the assembly. Unfortunately this resulted in uneven flow distribution between the legs, as well as local heating effects. Consequently, the sensor did not always control the solenoid valve properly, resulting in flooding of the plate and excess liquid exiting the plate along with the vapor stream.
Another design provided a reservoir between the liquid supply line and a common liquid header for the monogroove legs. Since the reservoir allowed liquid to be transported passively upon demand into the cold plate, the problem of uneven flow distribution was largely eliminated. There were, however, valve control problems under certain conditions, and the configuration was operable only as a cold plate, not reversibly for automatically supplying either heat or cold as needed according to system demands.
While there is considerable prior art relating to this technology, there appears to be none which teaches or suggests satisfactory solutions to these problems. This art includes, for example, U.S. Pat. No. 3,875,926 (Frank), issued Apr. 8, 1975, which teaches a plurality of heat pipes having a common manifold which supplies fluid to the heat pipes from a reservoir.
U.S. Pat. No. 4,583,587 (Alario et al.), issued Apr. 22, 1986, discloses a multi-leg heat pipe evaporator comprising a plurality of monogroove heat pipe legs welded together at their flanges to form a flat mounting plate. The monogroove heat pipe legs disclosed are of the type preferred for use in the present invention.
U.S. Pat. No. 4,515,207 (Alario et al.), issued May 7, 1985, discloses a monogroove heat pipe design of similar type.
U.S. Pat. No. 4,067,237 (Arcella), issued Jan. 10, 1978, discloses a heat pipe combination wherein two heat pipes are combined in opposing relationship to form an integral unit such that the temperature, heat flow, thermal characteristics, and temperature-related parameters of a monitored environment or object exposed to one end of the heat pipe combination can be measured and controlled by controlling the heat flow of the opposite end of the het pipe combination.
U.S. Pat. No. 4,492,266 (Bizzell et al.), issued Jan. 8, 1985, discloses a system including an evaporator 12 connected to a heat exchanger 26 from which liquid is pumped by means of pump 11 to the evaporator 12.
U.S. Pat. No. 4,495,988 (Grossman), issued Jan. 29, 1985, discloses a controlled heat exchanger system comprising a controller adapted to control the vapor pressure in the vapor chamber.
U.S. Pat. No. 4,635,709 (Altoz), issued Jan. 13, 1987, discloses a dual mode heat exchanger 10 for cooling airborne electonics 12 through a cold plate 14. The heat exchanger either radiates heat to air through radiator fins 18 or absorbs heat by evaporative cooling. The liquid coolant contained in grooves 16 of the cold plate 14 boils at a preselected temperature and thereby absorbs heat energy. Vapor released by the boiling liquid is exhausted through a hydrophobic filter membrane 24.
Other patents of possible interest include: U.S. Pat. No. 3,741,289 (Moore), issued June 26, 1973; U.S. Pat. No. 4,414,961 (Luebke), issued Nov. 15, 1983; U.S. Pat. No. 4,566,527 (Pell et al.), issued Jan. 28, 1986; U.S. Pat. No. 3,958,627 (Edelstein), issued May 25, 1976; U.S. Pat. No. 4,457,059 (Alaria et al.), issued July 3, 1984; U.S. Pat. No. 4,470,451 (Alario et al.), issued Sept. 11, 1984; U.S. Pat. No. 4,520,865 (Bizzell), issued June 4, 1985; U.S. Pat. No. 4,545,427 (Alario et al.), issued Oct. 8, 1985; U.S. Pat. No. 4,565,243 (Ernst et al.) issued Jan. 21, 1986; U.S. Pat. No. 4,616,699 (Grote), issued Oct. 14, 1986; U.S. Pat. No. 4,627,487 (Basiulis), issued Dec. 9, 1986; U.S. Pat. No. 4,632,179 (Meijer et al.), issued Dec. 30, 1986; and U.S. Pat. No. 4,653,471 (Takeuchi et al.), issued Mar. 31, 1987.
A need therefore remains for a new and improved monogroove plate heat pipe assembly, and in particular for an improved liquid supply control apparatus and method for such as assembly which effectively provides for automatic operation in both heating and cooling modes according to system needs. Such a method and apparatus should therefore automatically determine whether liquid should be supplied to or drained from the heat pipe assembly as a function, respectively, of whether heat is being supplied to it or removed from it. Further, the liquid needs to be managed such that neither flooding nor localized drying takes place in any of the legs in the heat pipe assembly. Preferably, the method and apparatus will also include appropriate control logic for carrying into effect the automatic operation of the system as either an evaporator or condenser for the working fluid, consistently with these other requirements and needs.